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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * dm-snapshot.c
3 *
4 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
5 *
6 * This file is released under the GPL.
7 */
8
9#ifndef DM_SNAPSHOT_H
10#define DM_SNAPSHOT_H
11
Mikulas Patocka586e80e2008-10-21 17:44:59 +010012#include <linux/device-mapper.h>
Alasdair G Kergonca3a9312006-10-03 01:15:30 -070013#include "dm-bio-list.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include <linux/blkdev.h>
Alasdair G Kergonca3a9312006-10-03 01:15:30 -070015#include <linux/workqueue.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016
17struct exception_table {
18 uint32_t hash_mask;
Milan Brozd74f81f2008-02-08 02:11:27 +000019 unsigned hash_shift;
Linus Torvalds1da177e2005-04-16 15:20:36 -070020 struct list_head *table;
21};
22
23/*
24 * The snapshot code deals with largish chunks of the disk at a
Milan Brozd74f81f2008-02-08 02:11:27 +000025 * time. Typically 32k - 512k.
Linus Torvalds1da177e2005-04-16 15:20:36 -070026 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070027typedef sector_t chunk_t;
28
29/*
30 * An exception is used where an old chunk of data has been
31 * replaced by a new one.
Milan Brozd74f81f2008-02-08 02:11:27 +000032 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
33 * of chunks that follow contiguously. Remaining bits hold the number of the
34 * chunk within the device.
Linus Torvalds1da177e2005-04-16 15:20:36 -070035 */
Alasdair G Kergon028867a2007-07-12 17:26:32 +010036struct dm_snap_exception {
Linus Torvalds1da177e2005-04-16 15:20:36 -070037 struct list_head hash_list;
38
39 chunk_t old_chunk;
40 chunk_t new_chunk;
41};
42
43/*
Milan Brozd74f81f2008-02-08 02:11:27 +000044 * Funtions to manipulate consecutive chunks
45 */
46# if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
47# define DM_CHUNK_CONSECUTIVE_BITS 8
48# define DM_CHUNK_NUMBER_BITS 56
49
50static inline chunk_t dm_chunk_number(chunk_t chunk)
51{
52 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
53}
54
55static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
56{
57 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
58}
59
60static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
61{
62 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
63
64 BUG_ON(!dm_consecutive_chunk_count(e));
65}
66
67# else
68# define DM_CHUNK_CONSECUTIVE_BITS 0
69
70static inline chunk_t dm_chunk_number(chunk_t chunk)
71{
72 return chunk;
73}
74
75static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
76{
77 return 0;
78}
79
80static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
81{
82}
83
84# endif
85
86/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070087 * Abstraction to handle the meta/layout of exception stores (the
88 * COW device).
89 */
90struct exception_store {
91
92 /*
93 * Destroys this object when you've finished with it.
94 */
95 void (*destroy) (struct exception_store *store);
96
97 /*
98 * The target shouldn't read the COW device until this is
99 * called.
100 */
101 int (*read_metadata) (struct exception_store *store);
102
103 /*
104 * Find somewhere to store the next exception.
105 */
106 int (*prepare_exception) (struct exception_store *store,
Alasdair G Kergon028867a2007-07-12 17:26:32 +0100107 struct dm_snap_exception *e);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108
109 /*
110 * Update the metadata with this exception.
111 */
112 void (*commit_exception) (struct exception_store *store,
Alasdair G Kergon028867a2007-07-12 17:26:32 +0100113 struct dm_snap_exception *e,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 void (*callback) (void *, int success),
115 void *callback_context);
116
117 /*
118 * The snapshot is invalid, note this in the metadata.
119 */
120 void (*drop_snapshot) (struct exception_store *store);
121
122 /*
123 * Return how full the snapshot is.
124 */
125 void (*fraction_full) (struct exception_store *store,
126 sector_t *numerator,
127 sector_t *denominator);
128
129 struct dm_snapshot *snap;
130 void *context;
131};
132
Mikulas Patockacd45daf2008-07-21 12:00:32 +0100133#define DM_TRACKED_CHUNK_HASH_SIZE 16
134#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
135 (DM_TRACKED_CHUNK_HASH_SIZE - 1))
136
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137struct dm_snapshot {
138 struct rw_semaphore lock;
Mikulas Patocka72727ba2008-04-24 21:43:11 +0100139 struct dm_target *ti;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140
141 struct dm_dev *origin;
142 struct dm_dev *cow;
143
144 /* List of snapshots per Origin */
145 struct list_head list;
146
147 /* Size of data blocks saved - must be a power of 2 */
148 chunk_t chunk_size;
149 chunk_t chunk_mask;
150 chunk_t chunk_shift;
151
152 /* You can't use a snapshot if this is 0 (e.g. if full) */
153 int valid;
Alasdair G Kergonaa14ede2006-02-01 03:04:50 -0800154
155 /* Origin writes don't trigger exceptions until this is set */
156 int active;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157
158 /* Used for display of table */
159 char type;
160
Mikulas Patocka92e86812008-07-21 12:00:35 +0100161 mempool_t *pending_pool;
162
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163 struct exception_table pending;
164 struct exception_table complete;
165
Alasdair G Kergonca3a9312006-10-03 01:15:30 -0700166 /*
167 * pe_lock protects all pending_exception operations and access
168 * as well as the snapshot_bios list.
169 */
170 spinlock_t pe_lock;
171
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 /* The on disk metadata handler */
173 struct exception_store store;
174
Heinz Mauelshageneb69aca2008-04-24 21:43:19 +0100175 struct dm_kcopyd_client *kcopyd_client;
Alasdair G Kergonca3a9312006-10-03 01:15:30 -0700176
177 /* Queue of snapshot writes for ksnapd to flush */
178 struct bio_list queued_bios;
179 struct work_struct queued_bios_work;
Mikulas Patockacd45daf2008-07-21 12:00:32 +0100180
181 /* Chunks with outstanding reads */
182 mempool_t *tracked_chunk_pool;
183 spinlock_t tracked_chunk_lock;
184 struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185};
186
187/*
188 * Used by the exception stores to load exceptions hen
189 * initialising.
190 */
191int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
192
193/*
194 * Constructor and destructor for the default persistent
195 * store.
196 */
Mark McLoughlin4c7e3bf2006-10-03 01:15:25 -0700197int dm_create_persistent(struct exception_store *store);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
Mark McLoughlin4c7e3bf2006-10-03 01:15:25 -0700199int dm_create_transient(struct exception_store *store);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
201/*
202 * Return the number of sectors in the device.
203 */
204static inline sector_t get_dev_size(struct block_device *bdev)
205{
206 return bdev->bd_inode->i_size >> SECTOR_SHIFT;
207}
208
209static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
210{
211 return (sector & ~s->chunk_mask) >> s->chunk_shift;
212}
213
214static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
215{
216 return chunk << s->chunk_shift;
217}
218
219static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
220{
221 /*
222 * There is only ever one instance of a particular block
223 * device so we can compare pointers safely.
224 */
225 return lhs == rhs;
226}
227
228#endif